Deus Ex is a first person shooter with stealth and RPG-elements. Designed by Warren Spector and Harvey Smith and written by Sheldon Pacotti.

Made by Ion Storm, released 2000, this game is one of the best of all games.

Set in a dystopian world during the year 2052, the central plot follows rookie United Nations Anti-Terrorist Coalition agent JC Denton, as he sets out to combat terrorist forces, which have become increasingly prevalent in a world slipping ever further into chaos. As the plot unfolds, Denton becomes entangled in a deep and ancient conspiracy, encountering organizations such as Majestic 12, the Illuminati, and the Hong Kong Triads throughout his journey.

You can customize your character through nano-augmentations—cybernetic devices that grant characters supernatural powers.
For solving quests you get skill points. Skill points are used to enhance the abilities of the character, like lockpicking, hacking …
Weapons can be enhanced by weapon modifications that can be found or bought.
There's also a lot of interaction with NPCs. The inventory is limited.

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— For every complex problem, there is a solution that is simple, neat, and wrong. - HL Mencken